The invention relates to a radiation-cured, laminate label. The invention also relates to the radiation-cured, laminate label bound to a polyolefin-based plastic container. The invention further relates to a radiation-cured, flexible laminate packaging material. The invention also relates to a radiation-curable adhesive composition suitable for use in forming the laminate label and flexible laminate packaging material.
Label applications typically require the protection afforded by an overlaminate of clear film, such as laminate labels which are subjected to an excessive amount of abrasion or moisture. Specific examples include labels for water, milk and other beverage grade containers, as well as labels for food grade and pharmaceutical grade containers, that are subjected to moist environments, such as condensation caused by repeated trips into and out of refrigerators.
The laminate labels usually comprise an outer clear protective film bound to a face stock using a radiation-cured laminating adhesive. The protective film is usually formed from a polyolefin, such as polypropylene, but can also be formed from other suitable polymeric materials, such as polystyrenes or polyesters. A pressure sensitive adhesive is usually applied to the back of the face stock for bonding the laminate label to a container.
It has recently been found that when the radiation-curable laminating adhesive is applied to the face stock, radiation-curable monomers adsorb into the face stock. The face stock hinders or prevents curing of the monomers adsorbed therein and thus, the adsorbed monomers are not bound. Over time, these unbound monomers can undesirably migrate through the face stock, pressure sensitive adhesive layer, and through the polyolefin container to contaminate the contents of the container. This problem is especially prevalent in extended shelf life items, such as beverage and pharmaceutical containers. The radiation-curable monomers can cause an undesirable odor and/or taste in the container contents.
There is a need for a radiation-cured, laminate label which does not leach monomers into the contents of polyolefin containers.
A similar problem also exists in flexible laminate packaging materials which contain a polyolefin layer and use a radiation-curable adhesive to bond the layers together. Uncured radiation-curable monomers can migrate through the polyolefin layer in the same manner as polyolefin containers and undesirably contaminate the contents thereof. Thus, there is a need for a radiation-cured, flexible laminate packaging material which does not leach monomers into the contents thereof.
An objective of the invention is to provide a radiation-cured, laminate label which does not leach radiation-curable monomers into the contents of polyolefin containers.
Another objective of the invention is to provide a radiation-cured, flexible laminate packaging material which does not leach radiation-curable monomers into the contents thereof.
The above objectives and other objectives are surprisingly obtained by using a low-migration, radiation-curable adhesive composition formulated from carboxylic acid functional monomers.
The invention provides a novel laminate label adapted for use on plastic containers suitable for containing a pharmaceutical or food grade product. The laminate label comprises a substantially clear or translucent protective polymeric layer bound to a face stock by a radiation-cured adhesive composition formulated from a low-migration, radiation-curable adhesive composition comprising at least 50% of one or more radiation-curable, carboxylic acid functional monomers.
The invention also provides a novel labeled plastic container suitable for containing a pharmaceutical or food grade product comprising:
a walled structure comprising a polyolefin material defining an interior space suitable for containing a liquid or solid food product or pharmaceutical product; and
a laminate label bound to an outer surface of said walled structure. The laminate label comprises a substantially clear or translucent protective polymeric film bound to a face stock by a radiation-cured composition formulated from a low-migration, radiation-curable adhesive composition comprising at least 50% of one or more radiation-curable, carboxylic acid functional monomers.
The invention further provides a novel laminated flexible packaging material suitable for containing a pharmaceutical or food grade product comprising:
a polyolefin film defining an interior space suitable for containing a liquid or solid food product or pharmaceutical product; and
at least one other film bound to the polyolefin film by a radiation-cured adhesive composition formulated from a radiation-curable composition comprising at least 50% of one or more radiation-curable, carboxylic acid functional monomers.
The invention also provides a novel low-migration, radiation-curable adhesive composition comprising at least 50% of one or more radiation-curable, carboxylic acid functional monomers.